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High risk drugs afsha > Theophylline > Flashcards

Theophylline Flashcards

1
Q

Does smoking affect theophylline concentration

A
  • Dose adjustment may be needed if pt has started or stopped smoking during treatment
  • Smoking can INCREASE theophylline clearance, thus will need to increase dose
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2
Q

Where in the body is theophylline metabolised

A

Liver

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3
Q

3 conditions in which plasma-theophylline concentration increased

A

Heart failure
Hepatic impairment
Viral infections

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4
Q

When does plasma-theophylline concentration decrease

A

Smoking
Alcohol consumption

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5
Q

Why are differences in half life of theophylline important

A

Because it has a NTI - toxic dose is close to therapeutic dose

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6
Q

Indications: uniphyllin continus

A

Chronic asthma
Reversible airway obstruction
Severe acute asthma

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7
Q

Theophylline - cautions

A
  • Cardiac arrhythmias or other cardiac disease
  • Elderly (increased plasma theophylline concentration) (in adults)
  • Epilepsy
  • Fever
  • Hypertension
  • Peptic ulcer
  • Risk of hypokalaemia
  • Thyroid disorder
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8
Q

Explain why theophylline should be used with caution in elderly

A

○ Prescription potentially inappropriate (STOPP criteria) as monotherapy for COPD
○ Safer and more effective alternatives available
○ Risk of adverse effects due to narrow therapeutic index

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9
Q

SE that can result from B2-agonist therapy

A
  • Potentially serious hypokalaemia can result
  • Particular caution with severe asthma - this effect may be potentiated by concomitant treatment with theophylline and its derivatives, CCs, diuretics, hypoxia
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10
Q

What needs to be monitored in severe asthma and why

A
  • Monitor plasma-potassium concentration
  • Potentially serious hypokalaemia can result from B2-agonist therapy
  • Particular caution with severe asthma - this effect may be potentiated by concomitant treatment with theophylline and its derivatives, CCs, diuretics, hypoxia
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11
Q

Signs of overdose

A

○ Vomiting (may be severe and intractable)
○ Agitation
○ Restlessness
○ Dilated pupils
○ Sinus tachycardia
○ Hyperglycaemia
○ Severe hypokalaemia may develop rapidly

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12
Q

A patient presents with pinpoint pupils and hypoglycaemia. Could they be suffering from theophylline overdose?

A

No
Features of overdose include DILATED pupils and HYPERglycaemia

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13
Q

More serious effects of theophylline overdose

A

○ Haematemesis
○ Convulsions
○ Supraventricular and ventricular arrythmias

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14
Q

How is toxicity often delayed?

A

Usually prescribed as MR formulations, therefore toxicity can be delayed

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15
Q

Treatment of theophylline poisoning (not treating the symptoms that come with it)

A

Repeat doses of activated charcoal to eliminate theophylline, even if it has been more than 1 hour since ingestion, and especially if a MR preparation has been taken

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16
Q

Treating the symptoms of theophylline poisoning
- vomiting

A

Ondansetron may be effective for severe vomiting resistant to other antiemetics
Unlicensed use

17
Q

Treating the symptoms of theophylline poisoning
- hypokalaemia

A
  • Corrected by IV infusion of potassium chloride
  • May be so severe that it requires 60mmol/hour - high doses need ECG monitoring
18
Q

What might need to be monitored when correcting hypokalaemia from theophylline poisoning

A
  • Correcting hypokalaemia: give IV potassium chloride, for severe hypokalaemia it may need such high doses of up to 60mmol/hour
  • High doses need ECG monitoring
19
Q

Treating the symptoms of theophylline poisoning
- convulsions

A

Control with IV lorazepam or diazepam

20
Q

Treating the symptoms of theophylline poisoning
- agitation

A

May require sedation with diazepam

21
Q

Treating the symptoms of theophylline poisoning
- use of SABA

A

If the patient doesn’t suffer from asthma, SABA can be administered IV to reverse severe tachycardia, hypokalaemia and hyperglycaemia

22
Q

Use in pregnancy

A
  • Neonatal irritability and apnoea reported
  • Can be taken as normal during pregnancy as it is important that there is good asthma control
23
Q

Use in breastfeeding

A
  • Present in milk - irritability in infant reported, MR preparation preferable
    Can be taken as normal during BF
24
Q

Use in hepatic impairment

A
  • Caution - risk of increased exposure
  • Consider dose reduction
25
Q

Monitoring requirements

A

Therapeutic drug monitoring of plasma-theophylline concentration

26
Q

What plasma-theophylline concentration is required for satisfactory bronchodilation in most individuals?

A
  • 10-20mg/litre (55-110micromol/litre)
  • However, lower concentrations of 5-15mg/litre may be effective
27
Q

At what concentrations can adverse effects occur?

A
  • Within the range 10-20mg/litre (which is also the plasma-theophylline concentration required for satisfactory bronchodilation in most individuals)
  • Both the frequency and severity increase at concentrations above 20mg/litre
28
Q

When should plasma-theophylline concentrations be taken

A

5 days after starting oral treatment
At least 3 days after any dose adjustments
Blood sample usually taken 4-6hours after dose of MR preparation (sampling times may vary, consult local guidelines)

29
Q

A prescription comes in for oral theophylline but no brand is stated. What should you do?

A
  • Rate of absorption from MR preps can vary between brands
  • Contact prescriber and agree the brand to be dispensed
30
Q

Important considerations on prescribing theophylline for patients who have been discharged from hospital

A

Patients discharged from hospital need to be maintained on the brand on which they were stabilised on as an in-patient

31
Q

Beta blockers

A

Predicted to increase risk of bronchospasm when given with theophylline
Severe interaction - AVOID

32
Q

Amiodarone

A

○ Theophylline predicted to cause hypokalaemia (potentially increasing risk of torsade de pointes) when given with amiodarone
○ Severe interaction
No recommendation made

33
Q

Citalopram, escitalopram

A

○ Theophylline predicted to cause hypokalaemia (potentially increasing risk of torsade de pointes) when given with amiodarone
○ Severe interaction

34
Q

Use of COC with theophylline

A

○ Predicted to increase exposure to theophylline
○ Monitor and adjust dose
Moderate

35
Q

Erythromycin

A

○ Decreases clearance of theophylline; theophylline potentially decreases clearance of erythromycin
○ Adjust dose
○ Severe interaction

○ Also predicted to cause hypokalaemia (potentially increasing risk of torsade de pointes) when given with erythromycin
○ Severe interaction
○ No recommendation made

High risk drugs afsha (5 decks)

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